Liquid material such as medical liquids, cleaners, printing ink, pesticides and other chemicals are often stored in pails constructed of metal, plastic, or fiber. Often these pails have a flexible closure element such as the ones referred to as "Flexspot" manufacturing by Rieke Corporation of Auburn, Indiana which afford a directional pour spout which is collapsible for easy stacking of the pails.
These flexible closure elements come sealed from the factory and the diaphram must be removed from the outer end of the closure element or spout for dispensing liquid materials contained in the pail. Heretofore, the flexible closure elements have been pulled upwardly through an opening formed in the upper surface of the pail to provide access to the upper diaphram surface on the closure element and a knife, screwdriver, or other instrument was used to cut the diaphram from the end of the closure element.
Use of a knife to open a flexible closure often results in a jagged, uneven cut across the upper end of the closure element. This jagged, uneven cut prevents proper resealing of the spout by the cap furnished with the closure element. In addition, the jagged edge does not afford proper directional flow of liquid contained in the pail when the liquid is poured through the dispensing spout.
In addition internal pressure sometimes develops in the pail due to thermal expansion of the chemicals ccontained therein. Cutting of the closure element with a knife or similar instrument may result in spraying vapor and scattering contents of the container which may be hazardous to the person opening the container or persons in the surrounding area.
Heretofore, devices have been devised which were intended to open membrane-sealed plastic bottles. Such devices are disclosed in U.S. Pat. Nos. 3,402,855; 3,581,605; and 3,784,045.
Devices of the type disclosed in the aforementioned patents employed cutting blades of various configurations which failed to efficiently cut a smooth edged circular opening in membrane-sealed closure elements constructed of readily deformable plastic material. One of the devices employed a cylindrical cutting blade having a sharpened lower surface such that the lower extremity of the cutting blade contacted the upper surface of the closure element around the entire lower periphery of the cutting blade. Another of the devices employed a cylindrical cutting blade having a serrated lower edge, each of the serrations being sharpened on each edge of the triangular shaped serrations to form cutting edges. Another of the devices employed a plurality of diametrically opposed cutting blades having cutting edges on the leading and trailing edges of each of the blades.
Difficulty has been experienced in screwing devices having cylindrical and multiple blades onto a flexible externally threaded pour spout for severing the diaphram across the end of the pour spout without stripping threads on the exterior surface of the relatively soft flexible material. Further, difficulty has been encountered in the use of such perforating devices wherein cutting edges were provided on both the leading edge and the trailing edge of the cutting blade since the trailing edge of the cutting blade tended to cut into the periphery of the opening formed in the membrane upon removal of the blade holding device from the externally threaded closure element.
It should further be noted that U.S. Pat. No. 3,581,605 discloses a combined membrane piercing and extracting member mounted to retain the diaphram portion of the closure element which has been cut away in the cap. However, the membrane extracting member was rigidly secured to the cap member such that it was difficult to remove severed membrane members from the cap making the device impractical for reuse in opening containers of toxic chemical because of the danger that the user might contact the chemical.